Currently, only the slave sends pdelay_request, so only the master
is handling them.  However, only the slave called pp_hooks.handle_preq()
-- thus it was never called.

Waiting for a test session about this assignment to correctionfield
done by wr_handle_preq(), this removes a little duplication and ensures
the hook is always called.
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>